There are numerous businesses which require a plurality of items to be gathered to fill a customer order. These businesses vary from automotive parts wholesales to drive through restaurants. To illustrate the magnitude of the problem, with drive through restaurants statistics indicate that on average 10% of the orders contain an error. When items are missing from an order, it has a major adverse effect on customer relations. The customer has usually returned to his work or residential premises before it is discovered that a paid for item is missing. It is practically impossible for the business to verify whether the customer was actually shorted the item or is being fraudulent. The business can only do its best to mollify the annoyed customer in the hope of retaining the customer's patronage in future.
Systems have been developed for use in self service grocery stores, to verify customer orders by weighing individual items as the customer assembles the order. Such self service checkout systems are described in U.S. Pat. Nos. 4,373,133; 4,676,343; 4,787,467; and 5,191,749. Most grocery store items have bar codes. Bar code scanners are used to read bar codes on individual items, as the individual items are scanned they are concurrently weighed. The purpose of weighing each item is as a cross-check to ensure that the self service customer is not scanning a low priced item and substituting a high priced item. Each item scanned has an allowable weight variation of plus or minus a preset amount. With U.S. Pat. Nos. 4,373,133 and 4,787,467 the system totals the weight of all of the items. The customer's bag is weighed at the door as the customer exits the store, in order to ensure that the weight of the bag has not been changed by the addition of items between the checkout and the door.
Unfortunately, the teachings of these systems are not transferable to a drive through restaurant environment or other environments in which it is extremely rare for individual items to have bar codes. The foundation of the self-service systems is the weighing of individual items. The sum of the allowable weight variations on individual items renders unreliable the total weight of the order for any other purpose other than deterring tampering between the checkout and the exit.